Knee air bag modules play an increasingly important role in vehicle safety engineering. A knee air bag module of this kind features a housing, an inflator and a knee air bag pleated into the housing, the bag can be inflated by the inflator (usually in the form of a gas generator). Like all typical air bags, the knee air bag features an outer skin which encloses a gas space. Frequently the air bag also features internal catch bands (or tethers) in order to restrict the depth of the expanded, outer skin. In this case, in the inflated state, at least one section of the outer skin of the knee air bag is positioned between one section of the instrument panel and the knee-shinbone region of the passenger to be protected. The purpose of the knee air bag during the vehicle impact is, firstly, to prevent contact between the instrument panel and the sensitive knee-shinbone region of the passenger to be protected, and secondly, to counteract a forward displacement of the pelvis of the passenger, which is of great importance, especially for non-belted passengers.
The housing of the knee air bag module can be disposed in the instrument panel so that its outlet opening is located essentially opposite to the region to be protected, so that the air bag upon actuation of the inflator moves essentially directly upon the knee-shinbone region of the passenger to be protected.
In addition, the “low mount” knee air bag modules are becoming increasingly important, in which the housing of the knee air bag module is arranged in a lower region of the instrument panel or in a transition region between instrument panel and the foot space covering. In this case the outlet opening of the housing does face the knee-shinbone region of the passenger to be protected. Frequently the outlet opening is located essentially in the horizontal plane, and thus essentially faces downward in the direction of the bottom of the vehicle. From this it follows that the knee air bag upon ignition of the inflator is initially ejected essentially downward and only thereafter is deployed slanting upward, so that upon complete deployment of the knee air bag, a protective section of the outer skin of the knee air bag is positioned between a section of the instrument panel and the knee-shinbone region of the passenger. From this it also follows that the outer skin of the knee air bag in its fully expanded state must exhibit a curved or kinked cross section. Further, it also follows that besides the protective section, the outer skin also features a fill and support section connecting the protective section with the housing, which generally does not come into contact with a body part of the passenger.
For example, from EP 2 376 313 B1, or WO 2013 070 524 A1 or EP 2 496 446 A1, generic knee protective apparatuses are known in which the fully expanded, outer skin of the knee air bag features an essentially L-shaped cross section. In this case the longer leg of the L forms essentially the protective section, and the shorter leg of the L, which extends, for example, essentially horizontally, forms the fill and support section.
In this kind of “low mount” knee air bag modules, at least in many vehicle geometries, there can be a risk of tipping of the knee air bag downward, and/or of an insufficient deployment along the instrument panel unless appropriate countermeasures are taken. This applies in particular when the knee air bag attachment occurs exclusively by means of the bolts of the gas generator. The known countermeasures can be, for example, the provision of external bands, guides and additional 3D-structures. However, these are generally expensive and markedly increase the required installation space requirement for the knee airbag assembly.
Proceeding from the above, the problem of the present invention is to improve a knee protection apparatus such that with simple means, a more stable and more reproducible deployment behavior of the knee air bag is attained.
This problem is solved by a knee protection apparatus and knee airbag module in accordance with the present invention.